1. Field of the Invention
The present invention relates to an image forming apparatus which forms an image on an image carrier according to a progress state of the image forming apparatus to perform maintenance operation, an image forming system and an image forming maintenance method.
2. Description of the Related Art
An image forming apparatus forms an image on an image carrier based on a job and performs a printing on a paper by transferring the image from the image carrier to the paper being conveyed. The image carrier is, for example, a photoreceptor on which a toner image is formed, or an intermediate transfer belt to which the toner image is transferred from the photoreceptor.
By the way, in accordance with duration of use of the image forming apparatus, image quality degrades, and operation failures, change in image quality, or the like, occur. For example, at an image forming unit, after an image on the image carrier is transferred, a toner which has not been transferred remains on an image carrier. Therefore, a cleaning blade is provided at the image carrier at a downstream side of a transfer region in a rotation direction, and residues such as a toner are swept and removed from the image carrier by the cleaning blade being made abut on a surface of the image carrier. However, if such cleaning removal operation is performed for a long period, friction resistance between the cleaning blade and the image carrier increases, which causes defects such as turn-up and chatter of the cleaning blade.
Meanwhile, it is known that the toner functions as a lubricant (friction reducing agent), and maintenance for reducing friction resistance of the image carrier is sometimes performed by making use of this function effectively to form an image patch on the image carrier when a printing distance becomes a predetermined distance.
Further, with an image forming apparatus, it is known that maximum density, gradation characteristics, tone, or the like, of an image which are parts of parameters of image quality fluctuate according to a cumulative number of printed sheets, or the like. Therefore, in order to achieve appropriate image quality, maintenance is regularly performed by forming an image patch on an image carrier, reading this image patch using an optical sensor, or the like, and executing image stabilization processing for adjusting a charging bias of a charging apparatus, an exposure light amount of an exposure apparatus, a developing bias of a developing apparatus, or the like, according to the read result.
While each of the above-described maintenance can be performed between a previous sheet and a following sheet when normal cut paper is used, in a job using continuous paper, because there is no cut between sheets, it is necessary to interrupt the job to perform the above-described maintenance.
For example, Japanese Patent Laid-Open No. 2009-78886 discloses detecting abnormality, or the like, in image formation performed by a printer engine and cancelling printing or continuing printing according to a degree of the detected abnormality during printing using continuous paper.
However, if a job is interrupted during printing using continuous paper, a cycle of images does not become constant. There is a case where displacement of the cycle of images is required to fall within approximately 1 mm.
Further, if a paper is conveyed to prevent the continuous paper from being heated at a fixing unit while the job is interrupted, because it is impossible to restart printing at the same position due to an image writing timing, or the like, there is a problem that periodicity collapses and a useless interval is provided at the continuous paper. If the continuous paper is subjected to cutting/processing by cutting machine, or the like, in post-processing machine in post-process after printing, there is a problem that the cut/processed position is displaced from an original cut/processed position by processing being performed at the post-processing machine without being aware that the cycle of images is not constant.
The present invention has been made in view of the above-described circumstances, and is basically directed to alarming a user about maintenance operation while performing printing using continuous paper.